1、使用未初始化的内存
#include#include int main(void){ char *p; char c = *p; printf("\n [%c]\n",c); return 0;}
root@ubuntu:/home/naviwork/valgrind_use# valgrind --tool=memcheck ./a.out
==2054== Memcheck, a memory error detector==2054== Copyright (C) 2002-2012, and GNU GPL'd, by Julian Seward et al.==2054== Using Valgrind-3.8.1 and LibVEX; rerun with -h for copyright info==2054== Command: ./a.out==2054== ==2054== Use of uninitialised value of size 4==2054== at 0x80483F1: main (main.c:8)==2054==2、在内存释放后读写
#include#include int main(void){ char *p = malloc(1); *p = 'a'; char c = *p; printf("\n [%c]\n",c); free(p); c = *p; return 0;}
root@ubuntu:/home/naviwork/valgrind_use# valgrind --tool=memcheck ./a.out
==2131== Memcheck, a memory error detector==2131== Copyright (C) 2002-2012, and GNU GPL'd, by Julian Seward et al.==2131== Using Valgrind-3.8.1 and LibVEX; rerun with -h for copyright info==2131== Command: ./a.out==2131==[a]
==2131== Invalid read of size 1==2131== at 0x80484A5: main (main.c:14)==2131== Address 0x4199028 is 0 bytes inside a block of size 1 free'd==2131== at 0x4025FE9: free (vg_replace_malloc.c:446)==2131== by 0x80484A0: main (main.c:13)3. 从已分配内存块的尾部进行读/写
#include#include int main(void){ char *p = malloc(1); *p = 'a'; char c = *(p+1); printf("\n [%c]\n",c); free(p); return 0;}
root@ubuntu:/home/naviwork/valgrind_use# valgrind --tool=memcheck ./a.out
==2153== Memcheck, a memory error detector==2153== Copyright (C) 2002-2012, and GNU GPL'd, by Julian Seward et al.==2153== Using Valgrind-3.8.1 and LibVEX; rerun with -h for copyright info==2153== Command: ./a.out==2153== ==2153== Invalid read of size 1==2153== at 0x804847B: main (main.c:9)==2153== Address 0x4199029 is 0 bytes after a block of size 1 alloc'd==2153== at 0x40265DC: malloc (vg_replace_malloc.c:270)==2153== by 0x8048468: main (main.c:6)==2153==4、内存泄漏
#include#include int main(void){ char *p = malloc(1); *p = 'a'; char c = *p; printf("\n [%c]\n",c); return 0;}
root@ubuntu:/home/naviwork/valgrind_use# valgrind --tool=memcheck --leak-check=full ./a.out
==2179== Memcheck, a memory error detector==2179== Copyright (C) 2002-2012, and GNU GPL'd, by Julian Seward et al.==2179== Using Valgrind-3.8.1 and LibVEX; rerun with -h for copyright info==2179== Command: ./a.out==2179==[a]
==2179== ==2179== HEAP SUMMARY:==2179== in use at exit: 1 bytes in 1 blocks==2179== total heap usage: 1 allocs, 0 frees, 1 bytes allocated==2179== ==2179== 1 bytes in 1 blocks are definitely lost in loss record 1 of 1==2179== at 0x40265DC: malloc (vg_replace_malloc.c:270)==2179== by 0x8048428: main (main.c:6)==2179== ==2179== LEAK SUMMARY:==2179== definitely lost: 1 bytes in 1 blocks==2179== indirectly lost: 0 bytes in 0 blocks==2179== possibly lost: 0 bytes in 0 blocks==2179== still reachable: 0 bytes in 0 blocks==2179== suppressed: 0 bytes in 0 blocks==2179== ==2179== For counts of detected and suppressed errors, rerun with: -v==2179== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 11 from 6)5. 不匹配地使用malloc/new/new[] 和 free/delete/delete[]
#include#include #include int main(void){ char *p = (char*)malloc(1); *p = 'a'; char c = *p; printf("\n [%c]\n",c); delete p; return 0;}
root@ubuntu:/home/naviwork/valgrind_use# g++ main.c -g
root@ubuntu:/home/naviwork/valgrind_use# valgrind --tool=memcheck --leak-check=full ./a.out ==2201== Memcheck, a memory error detector==2201== Copyright (C) 2002-2012, and GNU GPL'd, by Julian Seward et al.==2201== Using Valgrind-3.8.1 and LibVEX; rerun with -h for copyright info==2201== Command: ./a.out==2201==[a]
==2201== Mismatched free() / delete / delete []==2201== at 0x4025BD6: operator delete(void*) (vg_replace_malloc.c:480)==2201== by 0x804867F: main (main.c:13)==2201== Address 0x42d3028 is 0 bytes inside a block of size 1 alloc'd==2201== at 0x40265DC: malloc (vg_replace_malloc.c:270)==2201== by 0x8048648: main (main.c:7)==2201== ==2201== ==2201== HEAP SUMMARY:==2201== in use at exit: 0 bytes in 0 blocks==2201== total heap usage: 1 allocs, 1 frees, 1 bytes allocated==2201== ==2201== All heap blocks were freed -- no leaks are possible==2201== ==2201== For counts of detected and suppressed errors, rerun with: -v==2201== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 17 from 6)6. 两次释放内存
#include#include int main(void){ char *p = (char*)malloc(1); *p = 'a'; char c = *p; printf("\n [%c]\n",c); free(p); free(p); return 0;}
root@ubuntu:/home/naviwork/valgrind_use# valgrind --tool=memcheck --leak-check=full ./a.out
==2221== Memcheck, a memory error detector==2221== Copyright (C) 2002-2012, and GNU GPL'd, by Julian Seward et al.==2221== Using Valgrind-3.8.1 and LibVEX; rerun with -h for copyright info==2221== Command: ./a.out==2221==[a]
==2221== Invalid free() / delete / delete[] / realloc()==2221== at 0x4025FE9: free (vg_replace_malloc.c:446)==2221== by 0x804858B: main (main.c:12)==2221== Address 0x42d3028 is 0 bytes inside a block of size 1 free'd==2221== at 0x4025FE9: free (vg_replace_malloc.c:446)==2221== by 0x804857F: main (main.c:11)==2221== ==2221== ==2221== HEAP SUMMARY:==2221== in use at exit: 0 bytes in 0 blocks==2221== total heap usage: 1 allocs, 2 frees, 1 bytes allocated==2221== ==2221== All heap blocks were freed -- no leaks are possible==2221== ==2221== For counts of detected and suppressed errors, rerun with: -v==2221== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 17 from 6)
6、内存重叠
#include#include #include int main(void){ char buf[12] = {0}; memcpy(buf, buf + 5, 6); return 0;}
root@ubuntu:/home/naviwork/valgrind_use# valgrind ./a.out
==1886== Memcheck, a memory error detector==1886== Copyright (C) 2002-2012, and GNU GPL'd, by Julian Seward et al.==1886== Using Valgrind-3.8.1 and LibVEX; rerun with -h for copyright info==1886== Command: ./a.out==1886== ==1886== Source and destination overlap in memcpy(0xbe9306b0, 0xbe9306b5, 6)==1886== at 0x4028693: memcpy (mc_replace_strmem.c:878)==1886== by 0x804856F: main (main.c:9)